Gorgeous fish!
I personally would get a filter running on her tank now, to seed it, 3-4 weeks, just a bio filter of some sort. Then remove it an run it on the pond. Get some fish to "guinea pig" the pond for you, such as oscars or something else cheap that likes to eat. Feed them out in the pond for a month or so, take them out and then ad the ray. Using her current water is that useful, the bacteria that you want/need and is most accessible is in the sand and in the filter. You do want to match conductivity and pH though from tank to pond. Conductivity is more important b/c without it your ph reading will not be reliable.
Just my method. Not judging others.